The most directly visible consequence of new marijuana legalization laws is the emerging presence of medicinal and retail outlets providing marijuana access at point-of-sale (MAP) for the first time in the history of the United States. Other new laws decriminalizing the possession and recreational use of marijuana are further expanding the availability and normative acceptability of marijuana in all settings. Simultaneously, a second heretofore unseen product landscape is also emerging, based on growing demand for electronically vaporized (Vape) drug delivery systems capable of reducing the physical harm associated with inhaling combusted smoke from tobacco or other drugs like marijuana. Combined, these new MAP and Vape product landscapes are reshaping the real and perceived physical and legal risks of marijuana consumption, just as access to marijuana is dramatically expanding. Virtually nothing is known about the separate and combined impact new decriminalization laws and the emerging MAP and Vape landscapes will have on patterns of marijuana use. The proposed project will provide data to directly address this critical knowledge gap. It extends the use of an innovative methodology that has been the first to provide objective, real-time data on the degree to which individuals are exposed to point-of-sale products as they move through their daily activities, as well as the way accumulating exposure to socio-contextual factors (e.g., public and social use) affects attitudes and experimentation over time. Because a spectrum of marijuana laws are rolling-out sequentially across the US, we are proposing a naturalistic framework that will contrast longitudinal trends within and between 4 separate major metropolitan areas from different regions of the US, each characterized by different degrees of marijuana decriminalization, medicalization, and legalization. The proposed project couples our existing real-time point-of-sale exposure system with longitudinal ecological momentary assessment of normative beliefs and other attitudes about the risks and benefits of marijuana among N=4,400 non-users of marijuana from: 1) Denver, CO, 2) DC/MD/VA 3) New York, NY, and 4) New Orleans, LA. Quarterly follow-up assessments will assess use patterns across the study period. Our research team is well represented in each of these areas, and our team has pioneered the use of mobile technologies to document point-of- sale product landscapes and quantify individuals' exposure, reactivity, and behavior. Quantifying real-time exposure to MAP and Vape requires a multilevel system with both comprehensive point-of-sale data at the community level and location-based exposure data at the individual level. Entirely separate from the community-level data, participants who are blind to our primary focus on marijuana consent to continuous location tracking. Data are wirelessly synced to a secure server, where an advanced geographic information system links each person to their real-time environment. Thus, detailed exposure data are accurately quantified with very low participant burden. Right now we are witnessing the emergence of two novel product landscapes, each with complementary and profound implications for drug use in the US. Decriminalization and legalized use laws will further increase the prevalence of marijuana use in social and public contexts, something that has not been common for decades. The proposed work aims to specifically isolate the impact of these factors on emerging patterns of initiation among those who do not yet smoke marijuana. Teasing apart the evolving policy and product environments will make it possible to test our central hypothesis - that these structural changes will operate b shifting normative beliefs, reducing harm perceptions, and thus promoting experimentation.